BACKGROUND
Speed management and data-driven safety analysis are priority topics for the highway safety community. A key gap in the body of knowledge is limited understanding of traffic speed effects in the crash frequency and severity prediction models for most facility types. It is known that the severity of motor vehicle crashes increases with increasing traffic speed, and speed may influence crash frequency. However, speed is correlated with nearly every other factor in the American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM) crash frequency and severity prediction methods. As a result, current prediction approaches do not seem to incorporate traffic speed effects well and may even show counterintuitive results.
Improving the consideration of traffic speed effects in the models may result in more realistic and insightful results. Given the correlation of traffic speed with other roadway and intersection features, innovative methods of quantifying speed effects in crash prediction methods in addition to regression modeling should be considered. Research is needed to find ways to incorporate traffic speed effects into HSM crash prediction models to make them more accurate and better suited toward developing designs based on the Safe System Approach.
OBJECTIVE
The objective of the research is to develop implementable methods to incorporate the effects of traffic speeds on the prediction of crash frequency and severity. The proposed methods should be applicable to different roadway facility types, in a format compatible with HSM methods to support the work of state departments of transportation (DOTs) and other users of the manual.
Accomplishment of the project objective will require at least the following tasks.
TASKS
Task descriptions are intended to provide a framework for conducting the research. The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and subaward time. Proposals must present the proposers' current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objective.
PHASE I
Task 1. Conduct a comprehensive review of domestic and international research, guidance, models, and other innovative approaches with the potential to address traffic speed effects in highway safety analysis. Summarize how speed is incorporated in related predictive tools. Identify gaps, limitations, and promising methodologies that could be incorporated in the HSM.
Task 2. Identify and evaluate data sources that could help develop crash prediction models incorporating speed effects (potential metrics include but not limited to mean, variance, and 85th percentile of operating speed). Develop a comprehensive data collection, management, and validation plan with considerations of data availability, replicability, transferability, and scalability. Recommend a feasible plan, to be implemented in Phase II, with risk assessment and contingency to utilize the datasets for model development and validation.
Note: A data archive plan is required and to be submitted with Interim Report No. 1 in Task 4.
Task 3. Develop modeling frameworks that can account for speed effects in crash frequency and severity analysis, including traditional statistical methods, and potentially other alternative approaches and advanced sampling methods, considering the ease of use by practitioners. Provide model characteristics, validation strategies, selection criteria, and recommended priority order of different facility types to be modeled.
Task 4. Prepare Interim Report No. 1 documenting the findings of Tasks 1 through 3 and provide an updated work plan for the remainder of the research no later than 8 months after the subaward is awarded. The updated work plan must describe the methodology and rationale for the work proposed for Phase II.
Note: Following a 1-month review of Interim Report No. 1 by the NCHRP panel, the research team will be required to meet with the NCHRP project panel via a virtual meeting to discuss the interim report. Work on Phase II of the project will not begin until authorized by the NCHRP.
PHASE II
Task 5. Execute the work plan, including data collection and model development work, according to the approved Interim Report No. 1.
Task 6. Validate models and perform sensitivity analysis using independent datasets not used in model development. Specify applicable ranges of key explanatory factors in the developed models. Evaluate model prediction performance across facility types, context classifications, functional classifications, and traffic conditions as appropriate.
Note: The research should clearly define divergences from the most recent HSM, explain their purpose and relative value, and provide guidance for practitioners and future researchers to reconcile differences and harmonize relevant applications and approaches. The research team should document how the scope of developed models relates to existing models and provide guidance on how practitioners should select between new and existing models where their scopes overlap.
Task 7. Prepare an annotated outline of the research report.
Task 8. Prepare Interim Report No. 2 that documents Tasks 5 to 7 and provide an updated work plan for the remainder of the research. The updated plan must describe the process and rationale for the work proposed for Phase III.
Note: Following a 1-month review of Interim Report No. 2 by the NCHRP, the research team will be required to meet in person in Washington, DC with the NCHRP project panel to discuss the interim report. Work on Phase III of the project will not begin until authorized by the NCHRP.
PHASE III
Task 9. Adapt the validated models into implementable procedures or quantitative tools/products that are compatible with HSM predictive models, calibration methods, and practitioner workflows. Develop step-by-step processes for incorporating speed effects into crash prediction and severity estimation. HSM users should be able to apply the methods in a way similar to what they currently do with the manual.
Task 10. Prepare a draft final report that documents the entire research effort, including sample problems, assumptions, effect sizes, data limitations, and other constraints (e.g., range for valid input fields, conditions that cannot be assessed with the methodologies because the data sources used to develop the method did not include these conditions), and any lessons learned, based on the approved annotated outline in Task 7 no later than 6 months before the subaward end date.
Task 11. Present the research findings to appropriate technical committees of AASHTO and TRB for comments and propose any revisions to NCHRP.
Note: The research team should anticipate making two presentations during the period of performance to appropriate technical committees at meetings of AASHTO and TRB. Revise the draft research report after consideration of review comments.
Task 12. Prepare the final deliverables including the following:
- Final report documenting the entire research process and findings;
- All raw and cleaned data collected and used in this research (data should be provided in as close to its raw form as possible, based on subaward or legal restrictions): input data sets, fused and integrated research data sets, data dictionaries, data models, etc.;
- Presentation with speaker notes; and
- A stand-alone technical memorandum titled “Implementation of Research Findings and Products.” See Special Note J for additional information. Additional funding may be available for a follow-up subaward on the implementation of the results.
Note: Following receipt of the draft final deliverables, the remaining 3 months shall be for NCHRP review and comment and for research agency preparation of the final deliverables.
SPECIAL NOTES
A. Revisions to the Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs are highlighted in yellow within that document.
B. Proposals must be submitted as a single PDF file with a maximum file size of 10 MB. The PDF must be formatted for standard 8 ½” X 11” paper, and the entire proposal must not exceed 60 pages (according to the page count displayed in the PDF). Proposals that do not meet these requirements will be rejected. For other requirements, refer to chapter IV of the instructions.
C. The Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs have been modified to include a revised policy and instructions for disclosing Investigator Conflict of Interest. For more information, refer to chapter IV of the instructions. A detailed definition and examples can be found in the CRP Conflict of Interest Policy for Subawardees. The proposer recommended by the project panel will be required to submit an Investigator Conflict of Interest and Disclosure Form as a prerequisite for subaward negotiations.
D. Proposals will be rejected if any of the proposed research team members work for organizations represented on the project panel. The panel roster for this project can be found at https://www.mytrb.org/OnlineDirectory/Committee/Details/7239. Proposers may not contact panel members directly; this roster is provided solely for the purpose of avoiding potential conflicts of interest.
E. Proprietary Products - If any proprietary products are to be used or tested in the project, please refer to Item 6 in the Information and Instructions for Preparing Proposals.
F. Proposals are evaluated by the NCHRP staff and project panels consisting of individuals collectively knowledgeable in the problem area. The project panel will recommend their first choice proposal considering the following factors: (1) the proposer's demonstrated understanding of the problem; (2) the merit of the proposed research approach and experiment design; (3) the experience, qualifications, and objectivity of the research team in the same or closely related problem area; (4) the plan for ensuring application of results; and, if relevant, (5) the adequacy of the facilities. A recommendation by the project panel is not a guarantee of a subaward. The National Academy of Sciences (NAS - the contracting authority for the National Academies of Sciences, Engineering, and Medicine) will conduct an internal due diligence review and risk assessment of the panel’s recommended proposal before subaward negotiations continue.
G. Copyrights - All data, written materials, computer software, graphic and photographic images, and other information prepared under the subaward and the copyrights therein shall be owned by the National Academy of Sciences. The subawardee and lower-tier subawardees will be able to publish this material for non-commercial purposes, for internal use, or to further academic research or studies with permission from TRB Cooperative Research Programs. The subawardee and lower-tier subawardees will not be allowed to sell the project material without prior approval by the National Academy of Sciences. By signing a subaward with the National Academy of Sciences, subawardees accept legal responsibility for any copyright infringement that may exist in work done for TRB. Subawardees are therefore responsible for obtaining all necessary permissions for use of copyrighted material in TRB's Cooperative Research Programs publications. For guidance on TRB's policies on using copyrighted material please consult Section 5.4, "Use of Copyrighted Material," in the Procedural Manual for Subawardees.
H. The text of the final deliverable is expected to be publication ready when it is submitted. It is strongly recommended that the research team include the expertise of a technical editor as early in the project timeline as possible. See Appendix F of the Procedural Manual for Subawardees Conducting Research in the Transportation Research Board’s Cooperative Research Program for technical editing standards expected in final deliverables.
I. Proposals should include a task-by-task breakdown of labor hours for each staff member as shown in Figure 4 in the Information and Instructions for Preparing Proposals. Proposals also should include a breakdown of all costs (e.g., wages, indirect costs, travel, materials, and total) for each task using Figures 5 and 6 in the brochure. Please note that selected proposers are considered subawards to the National Academy of Sciences, the parent organization of TRB. TRB Cooperative Research Program subawards must comply with 2 CFR 200 – Uniform Administrative Requirements, Cost Principles, and Audit Requirements for Federal Awards. These requirements include a provision that proposers without a federally Negotiated Indirect Costs Rate Agreement (NICRA) or audited indirect rates shall be subject to a maximum allowable indirect rate of 15% of Modified Total Direct Costs (de minimis rate). Modified Total Direct Costs include all salaries and wages, applicable fringe benefits, materials and supplies, services, travel, and up to the first $50,000 of each lower-tier subaward. Modified Total Direct Costs exclude equipment, capital expenditures, charges for patient care, rental costs, tuition remission, scholarships and fellowships, participant support costs and the portion of each lower-tier subaward in excess of $50,000.
J. The required technical memorandum titled “Implementation of Research Findings and Products” should (a) provide recommendations on how to best put the research findings/products into practice; (b) identify possible institutions that might take leadership in applying the research findings/products; (c) identify issues affecting potential implementation of the findings/products and recommend possible actions to address these issues; and (d) recommend methods of identifying and measuring the impacts associated with implementation of the findings/products. Implementation of these recommendations is not part of the research project and, if warranted, details of these actions will be developed and implemented in future efforts.
The research team will be expected to provide input to an implementation team consisting of panel members, AASHTO committee members, the NCHRP Implementation Coordinator, and others in order to meet the goals of NCHRP Active Implementation: Moving Research into Practice, available at http://onlinepubs.trb.org/onlinepubs/nchrp/docs/NCHRP_ActiveImplementation.pdf
K. If the subawardee is proposed to conduct less than 50% of the total effort (by time or budget), then section five of the proposal should include (1) a justification of why this approach is appropriate and (2) a description of how the subawardee will ensure adequate communication and coordination with their lower-tier subawardees throughout the project.
L. All budget information should be suitable for printing on 8½″ x 11″ paper. If a budget page cannot fit on a single 8½″ x 11″ page, it should be split over multiple pages. Proposers must use the Excel templates provided in the Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs.
M. The National Academies have an ethical and legal obligation to provide proper attribution whenever material from other sources is included in its reports, online postings, and other publications and products. TRB will review all Cooperative Research Programs draft final deliverables using the software iThenticate for potential plagiarism. If plagiarized text appears in the draft final deliverable, the research team will be required to make revisions and the opportunity to submit future proposals may be affected.
